Making a circuit with two one-click switches, one closes the circuit, the other opens it


Joined Jun 8, 2013
Hello, new member here. I would like to clarify that I'm almost not educated at all in electronics even though I like it. I searched for some answers online but the problem is hard to put on few words, so when I found this forum I thought I could ask for help, actually a solution, or better, some instruction as I probably will not thorougly understand what I will be doing but I need to do it, and hopefully learn something while doing it. I know that the better way for me to learn is by studying but I know better that I would abandon the project if I had to start from the beginning.

I play Airsoft and I like to cutomize or modify my weapons. The majority of the existing weapons are completely mechanical and the gears work thanks to a motor connected to a battery. One of the cable is divided in two parts connected to the trigger: when the trigger is pulled, the contacts touch, the circuit is close and the battery gives power to the motor that spins the gear.

The full-auto mode is simple, the motor spins until the trigger is released and that's it, but I need to achieve even a singel shot mode. The single shot mode is a bit more complicated. Normally it is achieved by a mechanic system that, when a gear reaches a full cycle, moves a lever (Cut-off lever) that separate the contacts and opens the circuit, stopping the motor from spinning.

Now, for some reasons (high battery voltage (11.1 volts, 20-30 C) damages the trigger contacts, better trigger response, trigger moved in another spot), I would like to build a MOSFET system that can be connected to the battery and controls the current this way:
1) When the trigger is pulled, a microswitch(start) gets pressed. It should work with a single click or by staying pressed either way.
2) The microswitch(start) activates the MOSFET that gives energy to the motor.
3) The motor spins and makes the gears works until it completes a cycle. When it completes a cycle and the single shot is selected, a gear will move the cut-off lever that can be used to click another microswitch(end).
4) When clicked once, the microswitch(end) should cut the power off from the motor, regardless of the microswitch(start) position (still pressed or not).
5) After the cycle, the microswitch(start) can be pressed again or released and pressed again to start another cycle.

There are some tutorial on making a basic MOSFET that controls the opening and closing of the circuit, but I found none with this system I described. How should I do it? What MOSFET or resistors should I buy?
Can you make a timing diagram to help show the relationship between the “time” and the switch/firing states?

the horizontal axis would represent “time” and the vertical axis would represent the on/off/run/stop of the switches and firing states?
There would be one horizontal line per switch and one to show single shot or auto action..

Thread Starter


Joined Sep 22, 2020
Can you make a timing diagram to help show the relationship between the “time” and the switch/firing states?
I don't think I understood your question correctly. The firing modes are selected by the user whenever he wants to fire a single shot despite he keeps pressing the trigger or multiple shots